1. Field of the Invention
The present invention relates to a mount structure of an outboard motor.
2. Description of the Related Art
An outboard motor according to a prior art is described in, for example, U.S. Pat. No. 6,048,236. This outboard motor has a mount structure for attaching an upper case positioned below an engine cover to a hull. This mount structure includes a bracket, a sleeve, a bolt and a nut, a rubber collar, a rubber cap, an upper case, and a housing. The bracket has a through hole penetrating through the bracket forward and rearward. The sleeve is arranged along the front-rear direction at the rear of the bracket. The inner periphery of the sleeve communicates with the through hole of the bracket. The bolt is inserted in the inner periphery of the sleeve and the through hole of the bracket from the sleeve side (rear side). The nut is attached to an end portion of a shaft portion of the bolt projecting from the sleeve. Accordingly, the bracket and the sleeve are fastened together.
The rubber collar has a tubular shape. The collar is fixed to the sleeve so as to surround the sleeve. The collar is held on the upper case and the housing while being sandwiched by the upper case and the housing from the left and right. Accordingly, the bracket and the upper case are joined via the collar and the sleeve. The housing holds the collar in cooperation with the upper case, and covers the head portion of the bolt from the lateral side. The head portion of the bolt is opposed to a portion of the upper case and a portion of the housing in the front-rear direction across a gap. The rubber cap is covered on the head portion of the bolt. The cap has an elastic modulus higher than that of the rubber collar. The end surface of the cap is opposed to a portion of the upper case and a portion of the housing in the front-rear direction across a gap.
In the outboard motor according to the prior art described above, a propulsive force generated by a propeller is applied to the upper case. When the propulsive force generated by the propeller is small, the propulsive force is transmitted to the bracket from the upper case via the collar and the sleeve. At this time, vibration of the upper case is absorbed mainly by the rubber collar. On the other hand, when a forward propulsive force generated by the propeller is great, the collar is elastically deformed and the distance in the front-rear direction between the head portion of the bolt and the upper case and housing becomes shorter. Accordingly, the cap comes into contact with the upper case and the housing, and the propulsive force is transmitted to the bracket from the upper case via the cap and the sleeve. Then, when the propulsive force becomes small, the cap separates from the upper case and the housing again.